Circuit breaker for high voltage direct current



K. D. MADSEN 3,542,985 CIRCUIT BREAKER FOR HIGH VOLTAGE DIRECT CURRENTNov. 24 1970 Filed Jan. 25, 1968 INVENTOR.

1 L M AD 5 E N KRIQT'IAN DA) United States Patent U.S. Cl. 200147 3Claims ABSTRACT OF THE DISCLOSURE A circuit breaker is formed of twospaced apart annular outer electrodes, combined with which is a meansfor generating an axial magnetic flux. Means is provided inside theouter electrode which moves towards and away from centers of the outerelectrodes for bridging the spacing for closing and opening theelectrical connection between the outer electrodes. This means may be anan nular inner electrode operated by a bar passing between the outerelectrodes. Two parts of insulating material separate the outerelectrodes leaving a slot between them for the bar, and an electricallyinsulating shield is arranged between the parts and attached to the barto cover the opening between the parts when the inner electrode is movedto circuit-breaking position.

BACKGROUND OF THE INVENTION Field of the invention The invention relatesto a circuit breaker for high voltage direct current.

The prior art It is known to operate circuit breakers by usingprestressed springs or hydraulic and pneumatic means. In such operatingsystems, however, it is extremely difiicult to meet the desiredincreased demands for rapid operation of circuit breakers. As regardscircuit breakers for high voltage current there is also the special factthat the arc must have a considerable length before breaking isobtained. With known operating systems of the mentioned types it is hardto achieve in sufliciently short a time the necessary distance betweenthe contact surfaces which is necessary for breaking. By usingexplosives or some explosive gas for operating the breaker, very shortoperating times for circuit breakers can be obtained. When using such amethod of operation, however, it is difiicult to obtain severalbreakings in short intervals in high voltage circuit breakers which isnecessary for instance during rapid reclosing. Furthermore, circuitbreakers operated in such a way often have the disadvantage that theproducts of combustion will soil the operating cylinder and thesurrounding breaking parts. This can result in disturbances, forinstance on account of reduced insulating ability, particularly if theoperating cylinder is placed near the breaking means at the high voltagepotential. Because the operators often are being unaccustomed toexplosives, this type of circuit breaker also involves considerable riskof accidents. Operation is also usually rather noisy.

SUMMARY OF THE INVENTION The present invention relates to a circuitbreaker, preferably for high voltage current consisting of a number ofseries connected and substantially identical breaking devices. Such abreaking device consists of an outer, circular electrode provided withmeans for generating an axial magnetic flux and an inner electrodearranged inside the outer electrode. The invention is characterised inthat the inner electrode is arranged in a diametrical plane with respectto the outer electrode and that at least one of the elecrtodes isprovided with means'for obtaining closing and opening of the electricalconnection between the electrodes in said diametrical plane.

BRIEF DESCRIPTION OF THE DRAWINGS On the accompanying drawing FIGS. 1and 2 show two sections perpendicular to each other through a circuitbreaker with two series-connected breaking devices. FIG. 3 is anenlarged cross-section of a part of FIG. 1 and FIG. 4 is an enlargementof a part of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit breaker shown inFIGS. 1 and 2 has a casing 1, suitably of strong metal sheet which canwithstand the high pressure arising at opening. The casing has a cover 2at the top attached to the casing by bolts 3 or the like. The cover isprovided at the top with a blast plate 4 which yields if the pressureinside the casing increases so much that there is risk of the casingbursting. In order to prevent extinguishing medium splashing out if theblast plate should burst, a shield 5 is arranged below the blast plate.Below the cover the casting is provided internally with an insulatingcovering 6. The circuit breaker is placed on an insulator 7 whichcontains the operating apparatus necessary for operating the circuitbreaker.

The circuit breaker comprises two breaking devices arranged close toeach other and separated by two plates 8 of insulating material. Theright hand breaking device shown in FIG. 1 has an outer electrode 10.The series connection is obtained by two of the breaking devices havinga common inner electrode 11. The inner electrode is operated by a rod 12arranged between the plates 8 and extending into the insulator 7 to theoperating apparatus. When operating the inner electrode it moves inopenings 13 in the plates 8. In order to prevent the arcs in the twobreaking devices from coming into contact with each other during thebreaking process, a shield 14 of insulating material is attached to theinner electrode. The shield, together with the plates 8, makes asufiiciently long distance to prevent creeping current flash-overbetween the two breaking devices. In FIG. 2 the shield is shown withbroken lines in the closed position of the circuit breaker, the innerelectrode connecting the two outer electrodes. The dot and dash linesshow the shield in the open position of the circuit breaker when theinner electrode is in the middle of the outer electrodes.

The coil 15 for generating the axial magnetic flux is arrangedimmediately outside the outer electrode. The magnet coils for the twobreaking devices are series-connected so that the magnet flux has thesame direction in' both breaking elements. Each of the outer electrodesis connected to that network which is to be opened over the terminals 16and 17 which are arranged in the casing 1, as can be seen from FIG. 2.Due to this and to the fact that both the breaking devices are connectedto each other by means of the common inner electrode the current in onebreaking device will flow towards the inner electrode from one of theterminals over one of the outer electrodes, while in the second breakingdevice the current will flow from the inner electrode over the secondouter electrode to the second terminal. This means that the two arcsfrom the inner electrode 11 to the two outer electrodes 9 and 10 willrotate in opposite directions under influence of the magnetic flux fromthe coils 15. This substantially eliminates the torque which influencesthe circuit breaker due to electrodynamic forces.

To extinguish the arc the casing 1 is filled with a suitable medium,such as oil or clean water, and its free surface is designated 18. Theextinguishing substance must completely cover the breaking devices, butthere must be enough space for the gases which are generated duringbreaking. Particularly if oil is used, it is important to pay attentionto this fact as considerable quantites of gas are generated when the Oilaround the arc is heated.

1 claim:

1. Circuit breaker comprising two outer circular electrodes arrangedside by side and insulated and spaced from each other, each electrodebeing provided with means for generating an axial magnetic flux andmeans arranged inside the outer electrodes and movable towards and awayfrom the centers of the outer electrodes for bridging said space forclosing and opening the electrical connection between the outerelectrodes, said two outer electrodes are separated by two plates ofinsulating material arranged at distance from each other separating saidouter electrodes, said plates forming a slot between them, and a rod isarranged, movably mounted in said slot connected to the movable meansfor the operation thereof.

2. Circuit breaker according to claim 1 in which that part of the plateswhich is situated inside the outer electrodes has a radial opening forthe movement of the movable means.

3. Circuit breaker according to claim 2, in which an electricallyinsulating shield is arranged between the plates and attached to therod, thereby covering the opening in the plates when the movable meansis in the center of the outer circular electrodes.

References Cited UNITED STATES PATENTS 1,547,407 7/1925 Breeze 200-4472,150,564 3/1939 Rowe 1 200 147 2,820,122 1/1958 Teszner 200-l473,014,109 12/1961. Burger 200-141 X 3,128,361 4/1964 Kesselring 20015lFOREIGN PATENTS 523,890 4/1931 Germany. I

ROBERT s. MACON, Primary Examiner US. 01. X.R. 700-150, 151

